Hierarchical Ceramic Nanofibrous Aerogels for Universal Passive Radiative Cooling

Abstract

Solar-induced thermal challenges in buildings, cold chain logistics, and spacecrafts may be overcome by integrating passive radiative cooling (PRC) with aerogels having thermal insulation (TI). Herein, a universal radiative cooling silica aerogel (UCSA) is prepared through the simple regeneration and freeze-drying of commercial quartz fiber membranes. The optically engineered UCSA with a hybrid structure (silica nanofibers/microbeads) achieves remarkable solar reflectance (R_S.E. = 98.1%) and atmospheric transparency window emittance (ε_ATW = 92.1%) under Earth conditions, with a theoretical daytime cooling power of 103.3 W m⁻². In the harsh space environment, it exhibits ultrahigh average solar reflectance (R_S.E. = 99.1%) and broadband mid-infrared emittance (ε_MIR = 90%), achieving a cooling power of 354.1 W m⁻². Compared to single-functional approaches, UCSA synergistically integrates the PRC and TI performance for excellent thermal management capability. Moreover, this ceramic aerogel can resist temperatures up to 830 °C, safeguarding building occupants and spacecraft electronics. Furthermore, UCSA passes environmental aging and thermal vacuum outgassing tests for long-term viability both on Earth and in space. Finally, a USCA-covered box achieves an average sub-ambient cooling of 18.6 °C when exposed to sunlight. In summary, UCSA opens a path for energy-efficient and sustainable cooling strategy with universal applications.